CN217277841U - Flue gas analyzer with stable optical fiber signal transmission - Google Patents
Flue gas analyzer with stable optical fiber signal transmission Download PDFInfo
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- CN217277841U CN217277841U CN202220987937.2U CN202220987937U CN217277841U CN 217277841 U CN217277841 U CN 217277841U CN 202220987937 U CN202220987937 U CN 202220987937U CN 217277841 U CN217277841 U CN 217277841U
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Abstract
The utility model provides a stable flue gas analyzer of fiber signal transmission, including host computer and sampling pipe, the host computer includes light source, spectrum appearance and sampling pump, the sampling pipe includes the absorption cell, is connected with optic fibre between light source and absorption cell and spectrum appearance and the absorption cell, be provided with the vibrating device of one or more messenger's optic fibre quick vibration on the optic fibre. The utility model discloses a vibrating device makes optic fibre maintain the vibration, can make optic fibre rapid stabilization to can keep the stability of light signal at vibration in-process.
Description
Technical Field
The utility model belongs to gaseous detection area especially relates to a stable flue gas analyzer of fiber signal transmission.
Background
At present, various gas detection technologies based on optical absorption or emission methods are widely applied, and optical fibers are often used in instruments for detecting gases by adopting the optical technologies. The use of the optical fiber greatly improves the flexibility and the applicability of the design of the optical device, and the optical fiber can be adopted to isolate the high-temperature environment under the condition of ensuring the smoothness of light paths of the light source and the photoelectric sensor under the condition that the absorption cell needs high-temperature heating. For example, a flue gas analyzer using an ultraviolet differential method, capable of measuring SO in flue gas 2 NO and NO 2 The ultraviolet differential absorption signal of the pollutants is used for inverting the gas concentration. The ultraviolet differential absorption method needs to collect a zero gas spectrum as a reference spectrum, and then continuously collects a measured gas spectrum as an absorption spectrum for differential processing. Because the flue gas has high moisture content and SO 2 And NO 2 Is easy to dissolve in water, and the smoke is detected by heating the absorption cell to more than 120 ℃, namely the detection by a general heat-wet method. The working temperature of the ultraviolet light source and the spectrometer is generally not more than 60 ℃ at most, so the high-temperature absorption cell, the light source and the spectrometer are connected by adopting high-temperature resistant ultraviolet optical fibers. As the emission standard of the smoke pollutants is lower and lower, the detection limit of the instrument is required to be lower and lower, and the interference of the photoelectric signal is required to be less and better. The portable detecting instrument needs to be carried frequently, and the optical fiber is difficult to keep stable shape for a long time, which causes NO 2 The gas zero point is seriously drifted and often exceeds 5mg/m in a few minutes 3 The detection limit of the instrument can not reach 2mg/m required by national standard 3 The use of the thermal-wet flue gas analyzer is greatly limited. The same problem occurs when an optical fiber is used for gas detection for other applications.
SUMMERY OF THE UTILITY MODEL
The utility model discloses in the instrument to adopting the optical method of optic fibre to measure gas concentration, optic fibre causes the technical problem of optical signal interference to the measurement, provides a stable flue gas analyzer of optical signal transmission.
In order to achieve the above object, the utility model discloses a technical scheme be:
the utility model provides a stable flue gas analyzer of fiber signal transmission, includes host computer and sampling pipe, the host computer includes light source, spectrum appearance and sampling pump, the sampling pipe includes the absorption cell, is connected with optic fibre between light source and absorption cell and spectrum appearance and the absorption cell, be provided with the vibrating device that one or more messenger optic fibre vibrate fast on the optic fibre.
Preferably, the vibration device is a motor.
Preferably, the vibration device is one or more of an electromagnetic vibration device, a piezoelectric ceramic vibration device and a pneumatic vibration device.
Preferably, the vibration device has an amplitude of 0.10mm to 5.00mm and a vibration frequency of 1 to 10000 hz.
Compared with the prior art, the utility model discloses an advantage lies in with positive effect:
the utility model discloses increase vibrating motor on optic fibre outer protective layer, smoke gas analyzer is at the in-process of gathering photoelectric signal, and vibrating motor work makes optic fibre be in the vibration state to the form everywhere that makes optic fibre all is in the rapid change in-process, thereby has reduced the photoelectric signal drift that optic fibre stress slow change brought in very big degree. In practice NO 2 The zero drift is reduced to less than one third of the original zero drift, and compared with an ultraviolet differential system which is integrally designed by a spectrometer without optical fibers, a xenon lamp and an absorption cell, the zero indicating value fluctuation is basically the same, and the indicating value drift caused by the slow release stress of the optical fibers is basically and completely eliminated. And the preheating time of the instrument is greatly shortened, because the vibration can quickly release the original stress in the optical fiber, thereby eliminating the influence of the original stress change of the optical fiber.
Drawings
FIG. 1 is a schematic structural diagram of a conventional flue gas analyzer;
FIG. 2 is a schematic structural diagram of the core part of the flue gas analyzer of the present invention;
FIG. 3 is a difference absorption signal spectrum of a conventional flue gas analyzer after the zero calibration and the continuous extraction of zero gas for 3 minutes;
FIG. 4 is a graph of a differential absorption signal of a prior art flue gas analyzer 3 minutes after zeroing of the apparatus in the absence of optical fibers;
FIG. 5 is a diagram of a differential absorption signal spectrum of a prior art flue gas analyzer after a fiber is slightly bent;
FIG. 6 is a difference absorption signal map of 3 minutes after the utility model is installed with 3 vibration motors and calibrated to zero;
FIG. 7 is a graph showing the time-dependent changes in the measured flue gas concentration without the addition of a vibration motor and with the addition of 3 vibration motors;
in the above figures: 1. a host; 11. a light source; 12. a spectrometer; 13. a sampling pump; 2. a sampling pipe 21 and an absorption tank; 3. an optical fiber; 4. a vibration motor.
Detailed Description
For a better understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings and examples.
Example (b):
as shown in fig. 1, the structure of the ultraviolet flue gas analyzer is schematically illustrated, and the ultraviolet flue gas analyzer structurally comprises a host and a sampling tube, wherein the host comprises a light source, a spectrometer and a sampling pump, the sampling tube comprises an absorption cell, a xenon lamp light source and the spectrometer are connected to the absorption cell through a Y-shaped optical fiber, and the lengths of the optical fibers from the xenon lamp light source and the spectrometer to the absorption cell are all about 40 cm. In the embodiment, based on an ultraviolet flue gas analyzer of the model ZR-3211H of Qingdao Zhongrui intelligent instrument corporation, a vibration device is respectively additionally arranged on an optical fiber of the ultraviolet flue gas analyzer for testing. In this embodiment, 1 vibration motor and 3 vibration motors (as shown in fig. 2) are added, and then the test is performed and the standard deviation of the data is analyzed, which is compared with the case where no vibration motor is added. The vibration device may be an electromagnetic vibration device, a piezoelectric ceramic vibration device, a pneumatic vibration device, or the like, other than the motor, as long as the optical fiber is in a vibration state.
Repeated tests show that when the vibration motor is not added, the obtained differential signal can go through a process from instability to gradual stabilization after the optical fiber of the ultraviolet flue gas analyzer is deformed. The process is a process of gradually eliminating the internal stress of the optical fiber supporting structure, so that the shape of the optical fiber is gradually not changed any moreAnd thus the optical signal variation due to the change in the form of the optical fiber is gradually reduced until it is stabilized. However, this process is long, typically more than 3 hours or even more than 1 day, and the optical signal only changes slowly. Measurement of NO by differential absorption 2 The concentration instrument shows that the indication value continuously drifts, the zero point slowly changes, and the process can be repeated after the instrument is moved or the optical fiber is deformed due to vibration.
Fig. 3 is a differential absorption signal spectrum obtained after the ultraviolet flue gas analyzer based on the ultraviolet differential absorption principle performs zero calibration and continues to extract zero gas for 3 minutes without adding a vibration motor. In the figure, the horizontal axis represents the number of pixels of the spectrometer, and the pixel values correspond to the wavelengths of light. Wherein, the 1 st, 200 th, 400 th, 600 th, 800 th, 1000 th, 1200 th, 1400 th, 1600 th, 1800 th, 2000 th pixels correspond to light wavelengths 189.3, 225.7 th, 261.0 th, 295.0 th, 327.8 th, 359.2 th, 389.3 th, 418.1 th, 445.6 th, 471.6 th, 496.3nm respectively, the vertical axis is photon number for the spectral curve, the differential absorption signal amplified 100000 times for the standard gas differential absorption spectrum, the differential absorption signal amplified 1000000 times for the air differential absorption spectrum, and the air differential absorption spectrum is amplified 10 times more than the standard gas differential absorption spectrum for clearly seeing the change of the differential absorption signal. Wherein the slowly varying signals are filtered out by Fourier low frequency filtering. The pulse xenon lamp flashes synchronously, the integration time of the spectrometer is 15ms, the spectrum averaging times are 140, the spectrum sliding averaging times are 10, namely 1400 spectrum averaging is carried out, and the influence of white noise of the spectrometer can be effectively eliminated. In the figure, three curves are respectively a zero gas reference spectrum, an air absorption spectrum (the zero gas reference spectrum and the air absorption spectrum are basically overlapped), an air differential absorption spectrum and a standard gas differential absorption spectrum. Wherein the differential absorption spectra of the standard gas are NO and SO respectively from left to right 2 And NO 2 In which the NO concentration is 500ppm, SO 2 Concentration 400ppm, NO 2 The concentration is 400ppm, the atmospheric pressure is 101.3kp, the temperature of the absorption cell is 120 ℃, and the optical path is 70 cm.
Because the noise of the spectrometer and the xenon lamp can also cause differential absorption signals, the xenon lamp directly irradiates the spectrometer after the optical fiber is removed, and under the condition of the same other conditionsThe differential absorption signal generated by the spectral change caused by the optical fiber is removed. Fig. 4 shows the differential absorption signal 3 minutes after the zero calibration of the device in the state without optical fiber, which is basically generated by white noise and is characterized by fast change and small amplitude. Compared with the differential absorption spectrum with the optical fiber, the differential absorption signal generated by the spectral change caused by the optical fiber is very obvious, and the NO is practically treated 2 The measurement of (a) has a great influence. The standard deviation of the minute-average value of the nitrogen dioxide without the optical fiber structure is basically 0.5mg/m 3 Whereas the standard for the mean minute value after the optical fiber is attached is generally more than 1.5mg/m 3 So that NO is 2 The instrument detection limit of (2) exceeds 3.75mg/m 3 Cannot reach 2mg/m required by environmental ministry standards 3 The requirements of (1).
Fig. 5 shows a spectrum of a differential absorption signal of a slightly bent optical fiber of a conventional flue gas analyzer, wherein the length of the optical fiber is 400mm, the optical fiber is bent integrally, two ends of the optical fiber are fixed, and the displacement of the middle maximum deformation position is about 1 cm. It can be seen from the figure that the intensity of the spectral signal received by the spectrometer is slightly reduced after the optical fiber is slightly bent, and at the same time, an obvious differential signal waveform is generated, so that it can be confirmed that the light transmission efficiency of different wavelengths of light is reduced differently after the shape of the optical fiber is changed, so that the illustrated differential signal is generated, and a larger differential signal is generated after the slight shape change of the optical fiber, and the shape of the differential signal is similar to the waveform of the differential signal generated after 3 minutes by the optical fiber without a motor, so that the optical signal transmitted by the optical fiber is unstable due to the slight deformation of the optical fiber in the process of releasing the stress of the optical fiber without a vibration motor, and NO is generated 2 The measurement of (a) generates a large interference.
As shown in fig. 6, a graph of the differential absorption signal 3 minutes after 3 vibration motors were added and zero-corrected. It can be seen from the figure that, after 3 vibration motors are added, the differential signal generated by the original optical fiber is basically eliminated, and at this time, the differential absorption signal of the instrument is basically the same as the differential absorption signal generated without the optical fiber in fig. 4, and the influence on the instrument indication is also obviously reduced.
TABLE 1 statistical table of standard deviation of vibration motor, vibration motor and vibration motor
Table 1 is flue gas analyzer not with vibrating motor, install 1 vibrating motor additional and install the standard deviation statistical table under 3 vibrating motor three kinds of circumstances additional, and the contrast can be seen out, and flue gas analyzer is the biggest when ventilating the air when not adding vibrating motor, and the standard deviation is obvious to be reduced after adding 1 vibrating motor, and the standard deviation is minimum after installing 3 vibrating motor additional. The reason is that the length of the adopted optical fiber is 40cm, the whole vibration of the optical fiber is difficult to ensure by additionally arranging 1 vibration motor, and the optical signal drift still occurs in places without vibration, so the mean square error is improved, but the improvement degree is not large enough. And when 3 vibration motors are respectively arranged on the optical fibers, the vibration of the whole optical fiber is ensured, so that the effect is best.
FIG. 7 shows the measured NO when NO vibration motor is added and 3 vibration motors are added 2 Concentration versus time curve with minute on the abscissa and NO on the ordinate 2 Concentration of mg/m 3 Wherein the concentration is the minute mean. Wherein the dotted line is the change in the mean minute for the instrument with 3 vibration motors added and the solid line is the change in the mean minute for the instrument without vibration motors added. As can be seen from the figure, the minute-to-average fluctuation of the instrument is significantly reduced after the vibration motor is added.
As can be seen from the comparison, after the optical fiber is additionally provided with 3 vibration motors, the differential absorption signal generated by the optical fiber is basically eliminated, and the NO is actually measured 2 Standard deviation of minute mean of 0.6mg/m 3 The detection limit reaches 1.5mg/m 3 Meets the standards of the ministry of the environment (the ministry of the environment standard HJ 1131- 2 Detection limit is not more than 2mg/m 3 HJ 1132 and 2020 Portable ultraviolet absorption method for measuring nitrogen oxides in exhaust gas of stationary pollution sources, the detection limit of NO is not more than 1mg/m 3 ，NO 2 Detection limit is not more than 2mg/m 3 。)。
During the transmission of the optical fiber, if the shape is notThe stress changes and additional losses occur. Wherein the change in shape is primarily a change in the degree of curvature. The loss caused by bending of the fiber is called the bending loss. Any macroscopic deviation of the fiber axis from a straight line is referred to as bending or macrobending. Fiber bending causes coupling between modes in the fiber, which results in bending losses when the energy of the propagating mode is coupled into the radiating or leaky mode. This loss increases exponentially with decreasing radius of curvature. Another type of loss is due to the micron-scale lateral displacement of the fiber axis, known as microbending loss. Macrobending is mainly caused by changes in the profile of the fiber. The optical fiber must have a certain shape inside the instrument and is generally not placed perfectly straight. Even if the optical fiber is placed in a straight line, the optical fiber may assume a bent state inside the protective layer. And the contact point between the optical fiber and the protective layer may generate microbending loss due to the roughness of the surface of the contact point. It is found that the loss caused by bending the optical fiber varies with the wavelength. In the test, 200-plus 500nm light waves are adopted to pass through the ultraviolet optical fiber, when the bending degree of the optical fiber changes, the spectrum signal received by the receiving end can generate obvious overall change, the spectrum before and after the change of the optical fiber is subjected to differential processing, and after the slowly-changed signal is filtered, a larger differential signal can be generated. That is, when the optical fiber is bent, the transmission efficiency of light of different wavelengths varies inconsistently and without obvious regularity. The differential signal is used for detecting SO by using a differential principle 2 NO and NO 2 Has an effect on NO with a weak absorbance 2 The most severe is the effect. The bending of the optical fiber can not only generate differential signals, but also the shape change of the optical fiber can be continuously performed because the stress generated by the shape change needs a certain time to be eliminated after the optical fiber is bent, so the generated differential signals can be continuously changed, and the test shows that the generated differential signals generally need more than 3 hours to be relatively stable. In the process, NO of the analyzer based on differential absorption principle 2 The zero point of the magnetic field is shifted continuously, and the shift is more than 5mg/m within minutes 3 The application of gas analysis instruments with optical fibers is greatly limited.
On the outer protective layer of the optical fiberThe vibration motor is added, the vibration motor works all the time in the process of collecting photoelectric signals, the optical fibers are in a vibration state, so that all the stress of the optical fibers can be in the rapid change process, the motor rotating speed is more than 1000 revolutions per minute, usually 3000 revolutions are achieved, the amplitude is larger than 0.1mm, and therefore the stress change of the optical fibers is rapid periodic change. The acquisition period of the photoelectric signal is generally averaged for many times, and each acquisition period is more than 1 second on average, so that the optical signal change caused by the periodical change of the stress of the optical fiber in the acquisition period is also superposed, and the periodical signal is averaged after being superposed for many times, so that the photoelectric signal drift caused by the slow change of the stress of the optical fiber is greatly reduced. When the vibration motor is not additionally arranged, after the state of the optical fiber changes, the stress changes from fast to slow, the photoelectric signal drifts more and more slowly, the optical fiber changes obviously from the first few seconds to minutes, and all the optical fiber changes obviously to cause the zero point to drift obviously. After the vibration motor is additionally arranged, the change period of the photoelectric signal is extremely fast, and after multiple averaging, the zero indication value is basically not influenced by perception any more, so that the zero drift amount is greatly reduced. In practice NO 2 The zero drift is reduced to less than one third of the original zero drift, and compared with an ultraviolet differential system which is integrally designed by a spectrometer without optical fibers, a xenon lamp and an absorption cell, the zero indicating value fluctuation is basically the same, and the indicating value drift caused by the slow release stress of the optical fibers is basically and completely eliminated. Through testing, the indicating value drift is greatly reduced, the preheating time of the instrument is also greatly shortened, and the vibration can quickly release the original stress in the optical fiber, so that the influence of the original stress change of the optical fiber is eliminated.
For a long length of optical fiber, a plurality of vibration motors may be provided to vibrate the optical fiber everywhere. In practical tests, it is found that if the length of the optical fiber is long, a single vibration motor can only vibrate part of the optical fiber, so that the situation of the drift of the indication value can be improved, but the drift cannot be completely eliminated. After the number of the vibration motors is increased, the optical fiber has obvious vibration everywhere, and the data stability can be greatly improved.
Repeated tests show that the optical fiber is kept vibrating through the vibrating device, the optical fiber can be quickly stabilized, and the stability of an optical signal can be kept in the vibrating process.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in other forms, and any person skilled in the art may use the above-mentioned technical contents to change or modify the equivalent embodiment into equivalent changes and apply to other fields, but any simple modification, equivalent change and modification made to the above embodiments according to the technical matters of the present invention will still fall within the protection scope of the technical solution of the present invention.
Claims (4)
1. The utility model provides a stable flue gas analyzer of fiber signal transmission, includes host computer and sampling pipe, its characterized in that: the host computer includes light source, spectrum appearance and sampling pump, the sampling pipe includes the absorption cell, is connected with optic fibre between light source and absorption cell and spectrum appearance and the absorption cell, be provided with one or more vibrating device that make optic fibre quick vibration on the optic fibre.
2. The flue gas analyzer with stable optical fiber signal transmission according to claim 1, wherein: the vibration device is a motor.
3. The flue gas analyzer with stable optical fiber signal transmission according to claim 1, wherein: the vibration device is one or more of an electromagnetic vibration device, a piezoelectric ceramic vibration device and a pneumatic vibration device.
4. The flue gas analyzer with stable optical fiber signal transmission according to claim 1, wherein: the vibration amplitude of the vibration device is 0.10mm-5.00mm, and the vibration frequency is 1-10000 hz.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115877032A (en) * | 2022-12-08 | 2023-03-31 | 青岛众瑞智能仪器股份有限公司 | Method for detecting flue gas flow velocity by light interference scintillation method and novel flue gas flow velocity measuring instrument |
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- 2022-04-27 CN CN202220987937.2U patent/CN217277841U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115877032A (en) * | 2022-12-08 | 2023-03-31 | 青岛众瑞智能仪器股份有限公司 | Method for detecting flue gas flow velocity by light interference scintillation method and novel flue gas flow velocity measuring instrument |
| CN115877032B (en) * | 2022-12-08 | 2023-08-08 | 青岛众瑞智能仪器股份有限公司 | Method for detecting smoke flow velocity by optical interference scintillation method and smoke flow velocity measuring instrument |
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